The present invention relates to a projection display of a single-tube type CRT having excellent light utilization efficiency.
Recent CRT type projection displays typically adopt the composition shown in FIG. 1. In FIG. 1, the CRT type projection display includes a screen 1, projection lenses 2, CRTs 3 of three primary colors arranged in the crosswise direction, a deflection yokes 4 (hereafter referred to as DY), convergence yokes 5 (hereafter referred to as CY), focus yokes 6 (hereafter referred to as FY), and cathode electrodes 7. This display of the conventional system is suitable for projecting a large picture but requires three CRTs. Accordingly, the conventional display also requires circuits to drive the DY, CY, FY and the cathode electrode. In other words, the conventional display, has disadvantages of requiring a great number of parts and a high cost.
Since the crossing angle (in FIG. 1) of the projected beams of three primary colors is large (about ten degrees in a diagonal 40-inch display), there has been another disadvantage that white appears colored depending on the direction in which one looks at the screen.
There have been some cases where a single-tube CRT for the three primary colors is used to produce a color picture, then enlarge and project the picture, but this method has a disadvantage that the light utilization efficiency is reduced by the shadow mask to less than about 1/3.